Preheat oven to 350 F. Line an 8 x 8-inch baking pan with parchment paper
Make the base first; mix cake mix, butter, and 1 eggPat the dough into the pan evenly, the dough will be thick but easy to work with
Make a buttery layer
Cream together room-temperature cream cheese, 2 eggs, sugar, and vanilla Pour the buttery layer over the cake layer, and spread evenly Bake for 45 minutes or until edges are slightly brown, don't overbake.
The Center will be slightly jiggly but firm. Cool completely in the pan before cutting into squares.
Notes
After experimenting with different cake mixes, I prefer yellow, white and lemon. I also prefer to eat mine when they are still warm.